Hello, everyone.

This is Enta.

Does the drilling depth for rock bolts vary?

Rock bolts'The borehole length is 3.0 mThat's it.

For example, if the legal limit is 300□, then,Rope Material Lengthは

Projection + Formwork Thickness + Drilling Length = 0.1 m + 0.3 m + 3.0 m = 3.4 m

So, what about this?

 

This is clearly a frame that's over 300 mm.

Someone once told me, “If the actual measurement is 500 mm, doesn’t that mean the drilling depth will be 200 mm shorter?!!”

Well, that’s a point that’s often brought up, isn’t it?

This is what happens when you install the fence along the contours of the hillside rather than following the natural terrain, prioritizing aesthetics instead.

I guess this is fine in its own way, but personally, I think it's a waste of money.

Ground-level net + mortar + labor = a waste of money

That’s a different story if the rebar is thick and the terrain is very rugged.

Well, putting that aside, there are often issues with drilling depth in rock bolting work, but,

That's a spot people tend to point out, isn't it?

Leveling Mortar

Basically, the 200-mm section consists of soil and rock (natural ground).I believe that...

No, no! It's mortar!I bet that's what they'll say lol

The red part is definitely mortar.

In cases where the natural terrain is highly uneven, it is sometimes necessary to spray a low-strength mortar and then install formwork on top of it.

Alternatively, after backfilling and grading the natural ground, install formwork.

I think you’ll understand that, from a design perspective, it’s better to have something more solid than the original natural ground to support the structure.

"If the material used to fill in unevenness is of the same quality as or higher than the natural ground, it shall be regarded as natural ground."

 

Slope Protection Association, “Textbook on Construction Management Techniques for Slope Protection Works, Heisei 19, p. 189”

It is listed as shown above.

If we interpret the lower portion of the formwork—which became thicker than specified due to the sprayed concrete—as "natural ground," then,

The drilling length remains the sameThat’s how it works.

I think it wouldn't hurt to know a little about this topic.

 

See you later.